Laggy video in preview??

I dont remember last time when i made a video that it would lag in the preview window. I need to manually cycle through all the frames with the arrow key prior to playing it. Its mainly when i overlap the clips. Now my last video wasnt very high quality video, would that effect it? Is there something i can do with adjusting the preview video to make run more smoothly and not have to manually cycle through each frame?

You can adjust the preview quality I would select auto and let the soft ware find the best playback quality for your situation. This is only a get around for a bigger problem. The lower the resolution of the video the smoother it should play. If you have this problem when using "wasn't very high quality video", this means your hardware is struggling to cope, this could be either your hardware is very old or it's needs a good bit of house keeping done to it. OR a component is not working as it should.